The reason why Norway has such exciting nature of watercourses is the topographical shaping of the country, which is often steep and hilly. This provides a unique variation of both running and lentic water. In Norway, there are almost half a million lakes and waters of different sizes. The county of Finnmark alone, offers more than 180 000 water occurrences.

 

Environmental factors in freshwater
Non-biological environmental factors are important in deciding which species can survive and thrive in different freshwater localities. These are factors such as water quality, climate, currents, area, depth, substrate, and bottom topography.

 

Water quality is, to a large extent, a result of geological conditions within the precipitation area that surrounds a freshwater locality. Terrestrial vegetation and agriculture are also of influence. Water quality normally varies regarding variables such as pH, ionic composition, nutrients, and humic substances.

 

Temperature can also be limiting for the survival of species in a freshwater locality: most fish species can not survive if the bottom water freezes, and most amphibian species do not succeed in reproducing themselves in the northern regions.

 

Biodiversity in Limnic Environments
Variation in Norwegian freshwater nature provides an array of habitats for freshwater species. Water bodies and shore zones are important also for land living species: wetland birds, many bats and deer are examples of such species.

 

In Norway, 2794 totally or partly water living species are known, comprising animal groups such as fish, amphibians, insects, crustaceans and mites. Many mammals and birds are also connected to freshwater.

 

The approximately 45 species of freshwater fishes in Norway can be divided into two groups depending on their origin and direction of spreading; salmon, trout and char spread from west to east in the water courses, while grayling, gwyniad, perch, pike, and eel pout migrated from the east and into Norway. Introduction of fish from the 1800s and onwards led to a wider spreading of some species than their natural distribution.

 

Insects and crustaceans are the largest groups in terms of number of species in the freshwater localities. Insects represent more than half of the total biological diversity of freshwater animals. High numbers of plants, algae, and single celled organisms are also dependent on or strongly associated with freshwater.

 

Many species perform their whole life cycle in freshwater: fish, crustaceans, molluscs, several aquatic plants and algae. Some species live parts of their lives on shore and other parts in water, such as amphibians and many insects.

 

Species composition often varies from one freshwater locality to another. Non-biological environmental factors play a major role, but it is also a result of different spreading possibilities, immigration histories and competitional relations between species.

 

Natural spreading is limited by spreading barriers, and what is to become a barrier varies from species to species. For those groups that live their entire life in freshwater, areas of land or sea will become an insuperable barrier. Some organisms on the other hand, have seeds or eggs that can attach to birds or mammals, or can be transported by wind to new localities.

 

Other organisms, such as amphibians and many insects, can move over land or through the air. These are, however, limited by barriers such as terrestrial vegetation, topography, or long distances to the next suitable freshwater occurrence.=

 

Areas of freshwater are often varied and with exciting nature. Such areas are used frequently by children and adults, and provide nature adventures through fishing and outdoor activities. These areas are also useful in teaching. For many people the encounters with such nature areas are an important source to understand the nature.

 

The varied nature of watercourses are also important for tourism in many parts of the country. Eye catchers such as waterfalls and running waters provide important attractions. In combination with pure nature and intact biodiversity, Norwegian watercourse nature represents values that are rare in many parts of the world. For instance, seven of the 10 highest free-falling waterfalls in the world, are found in Norway.

 

Clean drinking water is an important resource to the society. Both biological and non-biological factors filtrate and purify water that is passing through the precipitation area on the way to drinking water reservoirs. Therefore, intact nature is a guarantee for pure water for human consumption.